Okay, so when I put in my copy of Galaga in my 7800, the Atari logo shows up, but then the screen either just goes completely black, or the screen just turns into a moving pattern of diagonal lines.
The cartridge is perhaps the least dirty Atari game I've ever seen. It literally looks like I took it out of the shrinkwrap and it still doesn't work. Other games work, by the way.
Any ideas?